1. Field of Invention
The present invention relates to a pretreatment processes that can be applied to heavy oil or other carbonaceous materials to change properties of the heavy oil or carbonaceous materials. More particularly, the present invention relates to pretreatment processes that can make a material, which otherwise would not be suitable for use in refining processes and the like, amenable to such processes. The pretreatment processes change properties of the heavy oil or carbonaceous materials, such as one or more of removing impurities or undesired content, reducing the viscosity, reducing molecular weight, reducing the specific gravity, and the like.
2. Description of Related Art
Many oils from natural sources as well as residue feeds, particularly bitumen (heavy oil), contain small quantities of heteroatoms (sulfur, oxygen and nitrogen), halides, and metals (such as nickel, vanadium and iron). Generally, removing these substances from the heavy oils or other carbonaceous materials increases the utility and adds value of the heavy oils or carbonaceous material, and can permit the heavy oil or carbonaceous material to be refined where otherwise refining would be difficult or impossible. However, refining and/or conversion of such crude materials is generally costly due to the cost and materials needed to process the crude materials. Furthermore, as environmental pressures continue to lower allowable emission levels in gas and diesel products, refining costs continue to rise.
One method for removing such heteroatoms, halides and/or metals from the crude materials is the well-known hydrotreating process. According to the hydrotreating process, the undesired atoms and elements are removed from the crude material by treating the crude material and related products with hydrogen in a packed-bed catalytic reactor. Such processes are well known in the art, and have been practiced extensively particularly in the refining industry.
For example, U.S. Pat. No. 5,779,992 and U.S. Pat. No. 5,591,325 each disclose apparatus and processes for hydrotreating heavy oils in a fixed-bed reactor packed with a hydrotreating catalyst. Such processes and apparatus are also disclosed, for example, in U.S. Pat. No. 5,466,363. Each of the afore-mentioned patents is incorporated herein in their entirety by reference.
An alternative method for improving the value and usefulness of heavy oils and other carbonaceous materials is the well-known hydrocracking method. The hydrocracking method is particularly useful for heavy oils and carbonaceous materials that have unusually high molecular weights, unusually high viscosity and/or unusually high specific gravities. The value of such crude materials could be improved by treatment processes that decrease their molecular weight, viscosity, and/or specific gravity. In such hydrocracking processes, a solid catalyst is used to crack, or reduce the molecular weight of, the crude material. This in turn generally provides a product with reduced viscosity and a reduced specific gravity. Such hydrocracking processes are also well-known in the art, and particularly, in the refining industry.
For example, U.S. Pat. No. 6,068,758 discloses a process for hydrocracking heavy oil using a catalyst. The catalyst comprises a mixture of hydrocracked residual asphaltene and metal-doped coke. U.S. Pat. Nos. 6,004,454 and 5,948,721 disclose processes for hydrocracking heavy oils using a disposing-type catalyst for catalytic hydrocracking of heavy oil and residuum in a suspension bed hydrocracking process. Other hydrocracking processes are disclosed in, for example, U.S. Pat. Nos. 4,999,328, 4,963,247, 4,766,099, and 4,252,634. All of the foregoing references are incorporated herein in their entirety by reference.
However, despite the various known treatment methods, many heavy oils and other carbonaceous materials can not be sufficiently pretreated to permit their further processing in current refinery operations. Thus, for example, many heavy oils and other carbonaceous materials can not be suitably subjected to catalytic hydrotreating or catalytic hydrocracking to permit their father refinement. For example, many of the heavy oils and carbonaceous materials result in unacceptable fouling of the catalyst or related processing equipment, thereby making their treatment economically unfeasible.
In an effort to address the problems in pretreating such heavy oils and carbonaceous materials for further refinery processing, an alternative method for treating such materials with a reducing gas and a supercritical water environment has been developed. The method produces results similar to hydrotreating, but it has not been commercially practiced due to the cost and difficulties of making the reaction work in conventional equipment. Such a process is disclosed in, for example, U.S. Pat. Nos. 4,485,003 and 4,840,725, the entire disclosures of which are incorporated herein by reference. In U.S. Pat. No. 4,485,003, a process is disclosed for producing liquid hydrocarbons from coal, comprising treating comminuted coal at 380° C. to 600° C. and at a pressure of 260 to 450 bar with water in a high pressure reactor to form a charged supercritical gas phase and a coal residue. Simultaneous with the water treatment, hydrogenation with hydrogen takes place in the presence of a catalyst. Subsequent to the reaction, the gas phrase is divided into several fractions by lowering its pressure and temperature, and energy and/or gas is generated from the coal residue. In a similar manner, U.S. Pat. No. 4,840,725 discloses a process for converting heavy hydrocarbon oil feedstocks to fuel range liquids. The process comprises contacting the high boiling hydrocarbons with water at a temperature of from about 600° F. to about 875° F. at a pressure of at least about 2000 psi in the absence of an externally supplied catalyst. The water and high boiling hydrocarbon form a substantially single phase system under the elevated temperature and pressure conditions utilized.